Good small monitor controller.

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Re: Good small monitor controller.

Post by Hugh Robjohns »

Ah yes, okay, that would work. I had speaker switching at the outputs in mind, but you could arrange to switch feeds from the left/right outputs across to the passive summing network instead.

Ideally, the switching should also ground the left/right outputs to prevent noise from the left/right speakers (and ground the summing resistors when not in use for the same reason) and you will still lose a bit of signal level through the passive summing, of course. A 4PDT switch would do it I think.

If you're going to use the passive attenuator schematic you linked above, i think it might be possible to use the input buffer resistors on each leg as the summing resistors too, but linking the two hot sides for both channels (and the two cold sides) to feed the hot (and cold) balanced mono output. The two sides of the volume pot would then be in parallel, halving the value, so the attenuation range would change, but I doubt that would be a major problem in the circumstances.
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Re: Good small monitor controller.

Post by ef37a »

Whichever way you cut it a passive controller is going to suffer from crosstalk, poor control law, level shifts, low input Z, high output Z, noise if the resistors get too high...All these factors can be traded off, one against the other but you cannot have it all good, all at once.

I knew all this of course when I bought the Mackie Passive but for my particular application, mostly source switching, it seems a good choice. What I did NOT know was how compromised it was in other respects and I still do not know the design rationale behind those compromises!

I continue to be amazed why some people are afraid a of a few op amps!

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Re: Good small monitor controller.

Post by Hugh Robjohns »

Sam, I had a quick sketch of an idea for your passive monitor controller, using the line feed resistors as the mono summers, and bypassing half the volume pot so that the control law and impedance remains roughly the same in both stereo and mono modes.

The minor complication is that the stereo/grot box switch needs to be a 12-way changeover in order to mute the unused outputs properly at the same time as routing the sum signals appropriately. There are 12-way push buttons... or you could use relays.

Anyway, for what it's worth, here's my sketch:
passive monitor control.png
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Re: Good small monitor controller.

Post by Sam Spoons »

Thanks for taking the time Hugh, I'll have a close look. I do have a couple of 4 pole double throw toggle switches I was planning to use but could consider other options.
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Re: Good small monitor controller.

Post by Hugh Robjohns »

I think I'd do all the switching with miniature sealed relays. It means the unit would need a small power supply, but you could use a ready-made wall-wart for that.
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Re: Good small monitor controller.

Post by Arpangel »

After all this talk I’m regretting ordering my TC, sounds like passive is verboten from what you all say! :D
All I want to do is turn my monitors down!
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Re: Good small monitor controller.

Post by Bob Bickerton »

The TC is just fine - simple big knob with a nice action and you won’t notice any problems.

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Re: Good small monitor controller.

Post by blinddrew »

What Bob said. ^^^
It's the ideal tool for the job you want to do.
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Re: Good small monitor controller.

Post by Hugh Robjohns »

Arpangel wrote:After all this talk I’m regretting ordering my TC, sounds like passive is verboten from what you all say! :D

You're really not good with decisions are you? Or technical descriptions, come to that... :lol:

A passive controller is absolutely fine when used appropriately. And inherently compromised when not used appropriately.

Your application is an appropriate use for a passive controller, and hopefully you can be trusted to install it correctly as previously advised. :ugeek:

The alternative is a well-designed active controller and that's going to cost you £200+ as a minimum....
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Re: Good small monitor controller.

Post by Arpangel »

Hugh Robjohns wrote:
Arpangel wrote:After all this talk I’m regretting ordering my TC, sounds like passive is verboten from what you all say! :D

You're really not good with decisions are you? Or technical descriptions, come to that... :lol:

A passive controller is absolutely fine when used appropriately. And inherently compromised when not used appropriately.

Your application is an appropriate use for a passive controller, and hopefully you can be trusted to install it correctly as previously advised. :ugeek:

The alternative is a well-designed active controller and that's going to cost you £200+ as a minimum....

Thanks, I’m using short leads, as I said, so it should be OK.
I know it’s not a good idea, but there are Youtube reviews that have said it sounds very good, more transparent than the Mackie for instance, but who knows, I’m sure it’ll be fine.
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Re: Good small monitor controller.

Post by Hugh Robjohns »

Arpangel wrote:Thanks, I’m using short leads, as I said, so it should be OK.

Yes, it should.

...there are Youtube reviews that have said it sounds very good, more transparent than the Mackie for instance...

I was very disappointed with the sound quality of the original Big Knob (I haven't listened to the later models). I found it a little noisy and veiled... but PW thought it was fine and used one for years very happily...
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Re: Good small monitor controller.

Post by Sam Spoons »

The original Big Knob is active, isn't the one discussed up-thread the BK Passive?
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